Image reader

An image reader comprising:

• a first image reading unit comprising:
• a first sensor configured to read an image on a first side of a document sheet being conveyed on a feeding path,
• wherein the first image reading unit is configured to start sending a first analog signal corresponding to the image read by the first sensor when the first image reading unit receives a first start signal;
• a second image reading unit comprising:
• a second sensor configured to read an image on a second side opposite to the first side of the document sheet being conveyed on the feeding path;
• and
• a second converter configured to convert a second analog signal corresponding to the image read by the second sensor into a second digital signal,
• wherein the second image reading unit is configured to start sending the second digital signal when the second image reading unit receives a timing signal after the second image reading unit receives a second start signal;
• and
• a processor configured to:
• send the first start signal to the first image reading unit;
• send the second start signal to the second image reading unit;
• continuously receive a first analog signal from the first image reading unit;
• convert the first analog signal into a first digital signal at predetermined time intervals;
• send the timing signal to the second image reading unit while the processor is not converting the first analog signal into the first digital signal;
• and
• receive the second digital signal from the second image reading unit while the processor is not converting the first analog signal into the first digital signal.